Layar is a really great meta-app for iPhone and Android that lets you see a lot of third-party geo-based augmented reality layers on your phone. A “layar” consists of a JSON webservice that provides Points of Interest to users. There is HttpHandler implementation available for .Net, but the Layar specification is so simple (in the good sense of the word) that I decided to just whip up my own in a MVC controller. Computing distances is pretty akward using LinqtoSQL and SQL Server, I use the DistanceBetween function described here. It is used by the FindNearestEvents stored procedure in the code below.